Abstract
Reduced genetic variation is a severe threat for long-term persistence of endangered animals. Immigration or translocation of new individuals may result in genetic rescue and increase the population viability of the endangered population or species. Unfortunately, studying genetic rescue in wild populations is very difficult, but breeding programs of endangered species can contribute to our knowledge of the diverse effects of genetic rescue. A recovery breeding program of common hamsters in the Netherlands enabled the study of genetic rescue in an endangered rodent as a few wild hamsters from two nearby and also highly threatened populations were added to the breeding stock. Litter size increased over the years, but no relation between inbreeding levels and litter size was found. Average litter size benefited from the genetic variation introduced by a hamster from Germany, but hamsters from Belgium had no effect on litter size. Rather than alleviating inbreeding depression the genetic rescue effect observed in this population seems to originate from the introduction of beneficial alleles by the German male. Breeding programs using several populations may increase the success of reintroductions and long-term persistence of these populations.
Highlights
Introduction of new males fromBelgium and Germany had a direct effect on genetic diversity, inbreeding coefficients and heterozygosity in captive-bred offspring
We focused in the breeding program on restoring and preserving as much genetic variation as possible and we hope that deleterious alleles will be purged after reintroduction in the wild (HEDRICK 2005)
Our study showed that the highly endangered Dutch hamster population suffered from inbreeding depression which negatively affected litter size, but this was only clarified after crossings with individuals from other populations as proposed by HEDRICK and KALINOWSKI (2000)
Summary
Belgium and Germany had a direct effect on genetic diversity, inbreeding coefficients and heterozygosity in captive-bred offspring. Heterozygosity in captive-bred off-spring increased, but this increase was almost comparable in both mixed breeding-lines and not used for further analysis. Despite the little difference in allelic diversity and heterozygosity in mixed breeding lines, a difference in litter size was found between breeding lines. This difference indicates that our observation is not a typical example of heterosis, as mixing of different inbred-populations (B1 and NL1 respectively G1 and NL1) did not show the same effect on litter size. The introduction of unrelated males decreased inbreeding coefficients in hybrid off-spring substantially. When the effect of inbreeding was analyzed simultaneously with the additive effects, inbreeding even had a positive effect on litter size
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